Siberian Silk Moth

**This organism is not known to be present in the United States but poses a threat. The Siberian silk moth is the most harmful defoliator of coniferous forests in North Asia. It does not yet occur in North America. It is able to attack and kill healthy plants and has been known to kill trees and forests across very wide areas. Outbreaks have occurred in China, Russia (particularly Asian and Siberian Russia and the Russian Far East), Japan, Mongolia, Poland and North and South Korea.

Siberian silk moth has a wide climate suitability range, making its survival likely in the northern US and Canada. Its host species include fir, Douglas fir, cedar, spruce, pine and hemlock. They have a 10-11 year outbreak cycle, with outbreak years often following dry weather. Outbreaks frequently cover millions of hectares, defoliation lasts two to three years and outbreaks are often followed by other forest insect pests and fires. Because of these factors, conifer mortality can approach 100% following a Siberian silk moth outbreak.

Pathways:

The most likely pathway for introduction of this species is on plant material imported to the US from countries where this pest is present. Siberian silk moth can be introduced unknowingly by sharing infested plant resources. All stages can be transported on plants moving in trade, particularly plants for planting, on cut branches, even on artificial and live Christmas trees.